1. Field of the Invention
The present invention relates to the field of display technology, and in particular to a low temperature poly-silicon thin-film transistor (TFT) substrate.
2. The Related Arts
Low temperature poly-silicon (LTPS) thin-film transistors (TFTs) have a great value of application and potential in the fields of active matrix liquid crystal display (AMLCD) and active-matrix organic light emitting diode (AMOLED) display that have a high resolution.
Compared to the amorphous silicon (a-Si) technology, LTPS TFT has a high mobility and excellent device stability. The mobility of LTPS TFT may get as high as tens to hundreds cm2/Vs, well suiting the needs for AMLCD and AMOLED having a high resolution. Thus, the LTPS display devices have a high response speed and various advantages of for example high brightness, high resolution, and low power consumption. Besides serving as a pixel switch, an LTPS TFT may also be used to construct a peripheral driving circuit to realize a system-on-chip arrangement.
However, when influenced by light irradiation, poly-silicon may cause instability of device, leading to an increase of leakage current and causing abnormal panel displaying. Thus, it is commonplace to form a shielding metal layer for shielding light before a TFT device is formed.
Referring to FIG. 1, a cross-sectional is given to illustrate the structure of a conventional LTPS TFT substrate. Before a TFT device is formed, a shielding metal layer 200 is first formed on a substrate 100. Then, the TFT device 300 is formed. The shielding metal layer 200 achieves light shielding for the area where the TFT device 300 is located thereby preventing a poly-silicon layer 400 contained in the TFT device 300 from being influenced by light irradiation and thus maintaining the stability of the TFT device 300.
However, forming a shielding metal layer 200 separately means one more photo-mask is needed in the manufacturing process. This extends the manufacturing process, lowering the manufacturing efficiency, and increases the manufacturing cost.